package leetcode.editor.cn;
//给定一个二叉树，找出其最大深度。 
//
// 二叉树的深度为根节点到最远叶子节点的最长路径上的节点数。 
//
// 说明: 叶子节点是指没有子节点的节点。 
//
// 示例： 
//给定二叉树 [3,9,20,null,null,15,7]， 
//
//     3
//   / \
//  9  20
//    /  \
//   15   7 
//
// 返回它的最大深度 3 。 
// Related Topics 树 深度优先搜索 广度优先搜索 二叉树 
// 👍 1542 👎 0


//leetcode submit region begin(Prohibit modification and deletion)

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 * int val;
 * TreeNode left;
 * TreeNode right;
 * TreeNode() {}
 * TreeNode(int val) { this.val = val; }
 * TreeNode(int val, TreeNode left, TreeNode right) {
 * this.val = val;
 * this.left = left;
 * this.right = right;
 * }
 * }
 */
class Solution15 {
    Integer maxDepth = 0;
    public int maxDepth(TreeNode root) {
        if (root == null) {
            return maxDepth;
        }
        int currentDepth = 1;
        depth(root,  currentDepth);
        return maxDepth;
    }

    private void depth(TreeNode root,int currentDepth) {
        if (root.left == null && root.right==null) {
            maxDepth = Math.max(currentDepth, maxDepth);
        }
        if (root.left != null) {
            depth(root.left,currentDepth+1);
        }
        if (root.right!=null){
            depth(root.right,currentDepth+1);

        }

    }

    public class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;

        TreeNode() {
        }

        TreeNode(int val) {
            this.val = val;
        }

        TreeNode(int val, TreeNode left, TreeNode right) {
            this.val = val;
            this.left = left;
            this.right = right;
        }
    }
}
//leetcode submit region end(Prohibit modification and deletion)
